Conventional communication devices have a main (or first) transmitter powered by a dedicated first power manager and a MIMO (or second) transmitter powered by a dedicated second power manager. See FIG. 1 and the related detailed discussion.
This conventional layout requires that the first power manager simultaneously powers all amplifiers in the first transmitter, and requires that the second transmitter simultaneously powers all amplifiers in the second transmitter.
This conventional layout has a problem because it is impossible to independently power (with different voltages) different amplifiers in the same transmitter. For example, if the first transmitter has a first amplifier for low bands and a second amplifier for high bands, then it is impossible to provide a high power voltage to the low band amplifier while simultaneously providing a low power level to the high band amplifier (and vice-versa).
Therefore, this conventional layout is very inefficient when performing uplink carrier aggregation transmissions and uplink MIMO transmissions.